The first antibiotic, penicillin, has a .beta.-lactam ring and showed an eminent efficacy against staphylococci. However, staphylococci can easily produce penicillinase (i.e., .beta.-lactamase) to inactivate penicillin. The staphylococci is called as penicillin-resistant bacteria. Against penicillin-resistant bacteria, for example, penicillinase-resistant penicillin- and cephem- antibiotics were developed and the problem involving penicillin-resistant bacteria seemed to be almost solved. However, a MRSA against which all .beta.-lactams have no effect developed.
The MRSA is widely resistant not only to penicillin- antibiotics but also to cephem- and aminoglycoside- antibiotics. Recently, as a result of overuse of cephem antibiotics of the third generation cephems which are weakly antibacterial to Staphylococcus aureus, the cephem-resistant Staphylococcus aureus selectively proliferated and spread in hospitals, and therefore, the cephem-resistant Staphylococcus aureus has become a serious object of public concern as infectious bacteria in hospitals. Vancomycin (VCM) or the like is currently used as an anti-bacterial agent against MRSA-infectious diseases; however, problems are that the sterilizing power of VCM is not very potent over a short duration and VCM has severe side effects such as ototoxicity and nephrotoxicity.
In order to promote anti-bacterial activity against MRSA, combinations of plural anti-bacterial agents have been studied, for example, a combination of an aminoglycoside and .beta.-lactam or a phosphomycin and a .beta.-lactam has been tried, however the effectiveness of the combinations is not sufficient.
Novel anti-bacterial agents are urgently needed to be developed that are based on a novel mechanism of function different from conventional mechanisms and effective against MRSA.